Add protobuf serialization to DisplayItemList

cc/playback/display_item_list.h

Index: cc/playback/display_item_list.h
diff --git a/cc/playback/display_item_list.h b/cc/playback/display_item_list.h
index 12ad23cdad58e25d32d487861aee8f666b153c25..970b73f6146c951c615d3eda2807622dec855606 100644
--- a/cc/playback/display_item_list.h
+++ b/cc/playback/display_item_list.h
@@ -13,6 +13,7 @@
 #include "cc/base/list_container.h"
 #include "cc/playback/discardable_image_map.h"
 #include "cc/playback/display_item.h"
+#include "cc/playback/display_item_list_settings.h"
 #include "skia/ext/refptr.h"
 #include "third_party/skia/include/core/SkPicture.h"
 #include "ui/gfx/geometry/rect.h"
@@ -22,7 +23,9 @@ class SkPictureRecorder;
 
 namespace cc {
 
-class DisplayItemListSettings;
+namespace proto {
+class DisplayItemList;
+}
 
 class CC_EXPORT DisplayItemList
     : public base::RefCountedThreadSafe<DisplayItemList> {
@@ -36,6 +39,15 @@ class CC_EXPORT DisplayItemList
       const gfx::Rect& layer_rect,
       const DisplayItemListSettings& settings);
 
+  // Creates a DisplayItemList from a Protobuf.
+  // TODO(dtrainor): Pass in a list of possible DisplayItems to reuse.
+  static scoped_refptr<DisplayItemList> Create(
+      const proto::DisplayItemList& proto);
+
+  // Creates a Protobuf representing the state of this DisplayItemList.
+  // TODO(dtrainor): Don't resend DisplayItems that were already serialized.
+  void ToProtobuf(proto::DisplayItemList* proto);
+
   void Raster(SkCanvas* canvas,
               SkPicture::AbortCallback* callback,
               const gfx::Rect& canvas_target_playback_rect,
@@ -102,7 +114,7 @@ class CC_EXPORT DisplayItemList
 
   scoped_ptr<SkPictureRecorder> recorder_;
   skia::RefPtr<SkCanvas> canvas_;
-  const bool use_cached_picture_;
+  const DisplayItemListSettings settings_;
   bool retain_individual_display_items_;
 
   gfx::Rect layer_rect_;